TITLE: GCN CIRCULAR NUMBER: 44590 SUBJECT: GRB 260509A: Infrared J and Hs observations with MDM/MIRAGE DATE: 26/05/12 20:45:37 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo@mit.edu> Geoffrey Mo (Carnegie/Caltech), K. De, V. Karambelkar, S. Ibrahim, D. Schiminovich (Columbia University) report: We observed the field of GRB 260509A (Gotz et al., GCN 44504) in the near-infrared J and Hs bands with the MDM InfraRed Astronomy inGaas Explorer (MIRAGE) instrument on the MDM 1.3 m telescope. Observations began at 2026-05-10T04:00:51 (+6.2 hours after the GRB trigger) in the J band and 2026-05-10T03:27:31 (+5.6 hours) in the Hs band, lasting 1560 s in J and 1260 s in Hs. The optical counterpart (O’Neill et al., GCN 44505; Saccardi et al., GCN 44506; Wu et al., GCN 44507; Alvarez et al., 44509; Zheng et al., GCN 44510; Lipunov et al., GCN 44512; Belkin et al., GCN 44513; Corcoran et al., GCN 44514; Bochenek et al., GCN 44516; Moskvitin et al., GCN 44563) is detected in the J filter at low significance and undetected in H band, with the following AB magnitudes: J = 20.91 ± 0.40, Hs > 19.6. MIRAGE is a new YJHs-band near-infrared imager for the MDM 1.3m telescope. We thank the MDM Observatory staff for supporting the observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44590. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...